JP2006144711A - Intake and exhaust controller for four cycle gasoline engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure required filling efficiency ηv and proper inside EGR rate m being suitable for ensuring compression self-ignition and torque while reducing pumping loss in accordance with change of an operation condition of an engine by enlarging margin of change of filling efficiency ηv. <P>SOLUTION: An exhaust valve driving means 62 for opening an exhaust valve 60 during an intake process when performing valve reopening operation and closing the exhaust valve 60 in a period from time close to bottom dead center to initial time in a compression process is provided. An intake valve driving means 43 for changing amount of valve opening of an intake valve 40 while opening the intake valve 40 in the vicinity of top dead center and closing the intake valve before bottom dead center in an operation region for performing at least valve reopening operation of the exhaust valve 60 is provided. Control means 120, 123 for controlling the intake valve driving means 43 to increase amount of valve opening of the intake valve 40 in a high load operation region when compared with a low load operation region among operation regions for performing valve reopening operation of the exhaust valve in accordance with engine load are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an intake / exhaust control system for a four-cycle gasoline engine, and more particularly, to an operation mode in which premixed compression auto-ignition combustion (HCCI) is performed, referred to as “compression auto-ignition” in this specification. The present invention relates to an intake / exhaust control device for a four-cycle gasoline engine.

In general, a technique is known that uses an internal EGR gas to improve the ignitability of an air-fuel mixture and ensure the EGR rate that is necessary in a wide operating region in order to enhance exhaust performance (for example, Patent Documents 1 and 2). In the configuration according to the prior art, the intake valve is opened during the exhaust stroke, or the exhaust valve is opened during the intake stroke, so-called internal EGR is realized.
Japanese Patent Laid-Open No. 9-25853 JP 2001-107759 A

  By the way, when performing compression self-ignition using internal EGR, when improving the performance of the engine in total, the mechanical compression ratio is increased as much as possible to secure internal EGR gas in a wide range of operation, It will be necessary to prevent knocking.

  However, in the techniques disclosed in Patent Documents 1 and 2, depending on the operation state, it was not possible to ensure the necessary charging efficiency and improve the torque and compression self-ignition performance, or prevent knocking. .

  The present invention has been made in view of the above problems, and in realizing compression self-ignition in a four-cycle gasoline engine, the mechanical compression ratio is increased as much as possible, and the boosting pressure is increased as much as possible while charging efficiency is increased. By expanding the variation range of the engine, the required filling efficiency and the appropriate internal EGR rate suitable for compression self-ignition and securing of torque can be reduced while reducing the pumping loss according to the change in the operating state of the engine. It is an object of the present invention to provide an intake / exhaust control device for a 4-cycle gasoline engine capable of ensuring the above.

  As a result of diligent research, the present inventor found that there is a correlation between the internal EGR rate and the boost pressure (intake pressure), which were normally considered to be less related, and completed the present invention. It was.

  That is, in order to solve the above-described problems, the present invention provides an internal EGR in-cylinder operation in a predetermined operating region of an engine by a resuming valve operation for reopening the exhaust valve in the intake stroke in addition to the valve opening operation in the exhaust stroke. In a four-cycle gasoline engine that is designed to perform compression self-ignition by increasing the temperature, the valve is opened during the intake stroke when the exhaust valve is restarted, and is closed within the period from the bottom dead center to the beginning of the compression stroke. An exhaust valve driving means for causing the intake valve to open at a position near the top dead center and to close before the bottom dead center at least in an operation region in which the exhaust valve is restarted. Intake valve drive means that can change the valve opening amount of the intake valve, and in the high load operation region of the operation region in which the resumption valve operation of the exhaust valve is performed according to the engine load, the intake valve is compared with the low load operation region. Large valve opening A suction and exhaust control device for a four-cycle gasoline engine, characterized in that a control means for controlling the intake valve driving means Kunar so. In this mode, when the exhaust valve is restarted during the intake stroke, the exhaust valve driving means opens during the intake stroke and closes within the period from the bottom dead center to the beginning of the compression stroke. The exhaust valve is restarted during the intake stroke by the exhaust valve driving means while suppressing the exhaust gas from being discharged from the exhaust passage and the exhaust gas to the intake passage side. Since the valve is closed within the period from the vicinity to the beginning of the compression stroke, the burned gas discharged in the exhaust stroke can be introduced into the cylinder in a relatively large amount as internal EGR gas in this valve opening operation. Thereby, in a state where the boost pressure (intake pressure) is as high as possible (a state close to the atmospheric pressure side), the range in which the charging efficiency and the internal EGR rate change is expanded, and the engine is changed according to the change in the engine operating state. Necessary filling efficiency suitable for load and proper internal EGR rate can be secured. As a result, it is possible to improve the compression self-ignition performance in the compression stroke while reducing the pumping loss. As a result, the compression self-ignition performance in the compression stroke can be improved while reducing the pumping loss. Moreover, since the structure which opens an exhaust valve in the intake stroke is employ | adopted, internal EGR is realizable at the timing which an exhaust valve does not interfere with a piston. Therefore, the geometric compression ratio can be increased as much as possible. In the present invention, the intake valve driving means is controlled by the control means, so that the exhaust valve restart operation is performed in the high load operation region in the low load operation region according to the engine load. In comparison, since the opening amount of the intake valve becomes larger, it is possible to reduce the amount of internal EGR gas introduced and suppress the excessive increase in the in-cylinder temperature on the high load side where knocking is likely to occur. As a result, it is possible to expand the region where compression self-ignition is possible to the high load operation region as much as possible.

  In a preferred aspect of the present invention, the opening amount of the intake valve is larger than the opening amount by the restart valve operation of the exhaust valve in at least the high load operation region of the operation region in which the restart valve operation of the exhaust valve is performed. It is set as follows. In this aspect, since the amount of fresh air can be ensured in the high load operation region, the charging efficiency can be ensured while suppressing the return of burned gas to the intake passage. In addition, since a large amount of fresh air is introduced, it is possible to reduce the in-cylinder temperature and contribute to the suppression of knocking.

  In the above aspect, within the operation region where the exhaust valve restart valve operation is performed, the opening amount of the intake valve is set to be equal to or greater than the valve opening amount due to the restart valve operation of the exhaust valve, and the ratio of both is set according to the operation state. It is preferable to make it change. In that case, since the EGR rate and the charging efficiency can be adjusted according to the operating state, the charging efficiency can be increased while suppressing the EGR rate on the high load side, and the low load operating region Then, it is possible to improve the compression self-ignition performance by increasing the EGR rate while increasing the in-cylinder temperature while ensuring the necessary charging efficiency. Therefore, it is possible to maintain the optimum EGR rate and filling efficiency while reducing the pumping loss in accordance with each operation region.

  In another aspect of the present invention, there is provided external EGR means for recirculating the exhaust gas cooled via the external EGR passage to the intake system, and knocking occurs in the operation region in which the resumption valve operation of the exhaust valve is performed. In an easy driving range, the EGR amount by the external EGR means is increased. In this aspect, the external EGR means introduces a relatively cool external EGR gas into the cylinder, thereby reducing the in-cylinder temperature and suppressing knocking.

  In yet another aspect of the present invention, the control means sets the opening amount of the intake valve relative to the high load operation region in the low load side operation region of the operation region in which the exhaust valve restart valve operation is performed. The intake valve driving means and the exhaust valve driving means are controlled so that the valve opening amount of the intake valve is gradually increased as it shifts from the operating area that is the boundary between both operating areas to the operating area on the high load side. . In this aspect, in the low load operation region and the medium load operation region (operation region that is a boundary portion between the low load operation region and the high load operation region), although the change rate of the boost pressure is large with respect to the charging efficiency, It becomes possible to increase the EGR rate, to realize reliable compression self-ignition by increasing the in-cylinder temperature, and to reduce the pumping loss. On the other hand, in the operation region from the middle load operation region to the high load side, the ratio of change in the boost pressure is small with respect to the charging efficiency, and by suppressing the EGR rate and the accompanying temperature rise, preventing knocking, It is possible to increase the filling efficiency. Here, in this aspect, the control means controls the intake valve drive means and the exhaust valve drive means so as to gradually increase the valve opening amount of the intake valve as it shifts from the medium load operation region to the high load operation region. It is possible to smoothly switch the balance between the in-cylinder temperature and the charging efficiency and obtain an optimal control state in accordance with the operating state.

  In yet another aspect, two intake valves and two exhaust valves are provided per cylinder, and one intake valve is closed in a low load operation region in an operation region in which the exhaust valve is restarted. The intake valve driving means and the exhaust valve driving means are configured so that the exhaust valve positioned diagonally with respect to the intake valve performing the valve opening operation is restarted. In this aspect, in the low load operation region, one of the intake valves is closed and the exhaust valve located on the diagonal line is restarted with respect to the intake valve that performs the valve opening operation, so that swirl occurs during intake. As a result, the air-fuel mixture in the cylinder is disturbed, and the mixing of the fresh air introduced from the intake passage and the burned gas introduced from the exhaust valve is promoted. For this reason, a rapid temperature rise can be achieved, and compression self-ignition can be performed more reliably. Moreover, since the mixing with the fuel is promoted by the disturbance, the fuel efficiency is improved and the lean combustion limit is improved.

  In a specific aspect of the present invention, the exhaust valve driving means includes a first exhaust cam that opens the exhaust valve in the exhaust stroke, a second exhaust cam that opens the exhaust valve in the intake stroke, and an exhaust valve from the second exhaust cam. A lost motion mechanism capable of interrupting drive transmission to the intake valve, and the intake valve driving means includes a variable valve opening amount mechanism capable of steplessly changing at least one of a valve lift amount and a valve opening period of the intake valve. I have.

  As described above, according to the present invention, in realizing compression self-ignition in a four-cycle gasoline engine, the mechanical compression ratio is increased as much as possible, while securing the internal EGR gas in a wide range of operation, There is a remarkable effect that knocking can be prevented.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram showing a schematic configuration of a four-cycle gasoline engine 10 according to an embodiment of the present invention, and FIG. 2 shows one cylinder of an engine main body 20 according to FIG. It is a cross-sectional schematic diagram which shows structures, such as an exhaust valve.

  With reference to the figure, the illustrated four-cycle gasoline engine 10 includes an engine body 20. The engine body 20 integrally includes a cylinder block 22 that rotatably supports the crankshaft 21 and a cylinder head 23 that is disposed above the cylinder block 22.

  The cylinder block 22 and the cylinder head 23 are provided with a plurality of cylinders 24. In the present embodiment, the compression ratio of each cylinder 24 is set to 12.

  Each cylinder 24 is provided with a piston 25 connected to the crankshaft 21 and a combustion chamber 26 formed in the cylinder 24 by the piston 25 in the same manner as a known configuration. The cylinder block 22 is provided with a crank angle sensor 27 that detects the rotational speed of the crankshaft 21.

  A fuel injection valve 28 that directly injects fuel into the combustion chamber 26 is provided at the side of each combustion chamber 26. An ignition plug 29 is provided at the top of each combustion chamber 26, and the plug tip faces the combustion chamber 26. An ignition circuit 29a capable of controlling the ignition timing by electronic control is connected to the ignition plug 29.

  The engine body 20 includes an intake system 30 that supplies fresh air into the cylinder 24 and an exhaust system 50 that exhausts burned gas burned in the combustion chamber 26 of the cylinder 24.

  The intake system 30 includes an intake pipe 31 for supplying fresh air into the cylinder 24, an intake manifold 32 communicating with the downstream side of the intake pipe 31, and a branch from the intake manifold 32 to the corresponding cylinder 24. And a branch intake pipe 33 to be connected. In the illustrated embodiment, each cylinder 24 is formed with a pair of intake passages 24a (see FIG. 1), and the downstream end of the branched intake pipe 33 corresponds to the intake passage of each cylinder 24. It is formed in two forks.

  An airflow sensor 34 is provided in the intake pipe 31 of the intake system 30. Each branch intake pipe 33 is provided with a multiple throttle valve 36 that is simultaneously driven by a common shaft 35. The multiple throttle valve 36 is configured to be opened and closed by an actuator 37 that rotationally drives the shaft 35.

  An intake valve 40 is provided in each intake passage 24 a provided in each cylinder 24. Each intake valve 40 is configured to be driven by a valve operating mechanism 41. The valve operating mechanism 41 includes a variable camshaft timing mechanism (VCT) 42 that can switch the opening timing (phase angle) of the intake valve 40 and a VVE that can change the lift amount (valve opening amount) of the intake valve 40 in a stepless manner. (Variable Valve Event) 43.

  FIG. 3 is a schematic plan view of the intake valve 40 and the exhaust valve 60 provided in the cylinder according to the embodiment of FIG.

  Referring to the figure, out of a pair of intake valves 40 provided in each cylinder 24, a valve stem 40a of one intake valve 40 is provided with a direct acting tappet 61. A VVL (Variable Valve Lift mechanism) 70 is provided on the valve stem 40a of the other intake valve 40.

  FIG. 4 is a perspective view showing a specific configuration of the valve mechanism 41 according to the embodiment of FIG.

  With reference to the figure, the valve operating mechanism 41 includes a camshaft 41a extending along the direction in which the cylinders 24 are arranged (see FIG. 1), and a VCT42 and a VVE43 are incorporated in the camshaft 41a. .

  The VCT 42 includes a rotor (input member) 42a fixed to the end of the camshaft 41a, a casing (output member) 42b disposed concentrically on the outer periphery of the rotor 42a, and the casing 42b. And a sprocket 42c disposed on the outer periphery of the sprocket 42 relatively rotatably. A chain 42d for transmitting driving force from the crankshaft 21 (see FIG. 2) is wound around the sprocket 42c. Further, a hydraulic oil chamber (not shown) is formed between the rotor 42a and the casing 42b, and the rotor 42a and the casing 42b are integrally rotated or relatively rotated by hydraulic control of the electromagnetic valve 42e. It can be switched to operation. Thus, the VCT 42 constitutes an operation timing variable mechanism that can simultaneously change the valve opening start timing and the valve closing timing of the intake valve 40. As will be described later, the electromagnetic valve 42e is drive-controlled by the VCT control means 122 of the ECU 100 as a control device, and the rotor 42a and the casing 42b are connected / disconnected by this drive control. It has become.

  Next, the VVE 43 includes a pair of intake cams 43 a and 43 b provided on each intake valve 40. One intake cam 43a is fixed to the camshaft 41a. The other intake cam 43b is attached to the camshaft 41a so as to be relatively rotatable. A sleeve-like cam journal 43c is concentrically fixed to the other cam 43b.

  In the present embodiment, one of the intake valves 40 arranged in pairs in each cylinder 24 is provided with a direct acting tappet 61 and the other has a so-called lost motion function. VVL70 which has is provided. Correspondingly, the intake cam 43b driven by the VVE 43 drives the tappet 61, and the intake cam 43a fixed to the cam shaft 41a drives the VVL 70 (see FIG. 3).

  5A and 5B are cross-sectional views showing the main part of the VVE in FIG. 4, where FIG. 5A shows the lift amount being 0 in the large lift control state, and FIG. 5B is the maximum lift amount in the large lift control state. (C) shows the time when the lift amount is 0 in the small lift control state, and (D) shows the time when the lift amount is maximum in the small lift control state.

  Referring to FIG. 4 and FIGS. 5A to 5D, in order to synchronize the intake cam 43b attached to the camshaft 41a so as to be rotatable relative to the camshaft 41a, An eccentric cam 43d provided for each cylinder 24 is fixed. As is apparent from FIGS. 5A to 5D, the eccentric cam 43d is eccentric with respect to the cam shaft 41a. An offset link 43e is rotatably attached to the outer periphery of the eccentric cam 43d. A protrusion 43f protruding in the radial direction is integrally provided on the outer peripheral portion of the offset link 43e. A connecting pin 43g parallel to the camshaft 41a passes through the projecting portion 43f, and one end of each of the link arms 43h and 43i is rotatable on both side surfaces of the offset link 43e by the connecting pin 43g. Is attached. One link arm 43h connects the offset link 43e and the intake cam 43b, and the other end of the link arm 43h is rotatable to the vicinity of the bulging portion of the intake cam 43b by a pin 43j parallel to the cam shaft 41a. It is connected to. The other link arm 43i is for connecting the offset link 43e to the eccentric shaft 43k that changes the phase of the offset link 43e. With respect to the end of the control arm 43m fixed to the eccentric shaft 43k, The other end is rotatably connected by a pin 43n parallel to the camshaft 41a.

  As shown in FIG. 4, a fan-shaped worm wheel 43p is fixed in the middle of the eccentric shaft 43k, and a worm gear 43q meshing with the worm wheel 43p is driven to rotate by a stepping motor 43r. Yes. As will be described later, the stepping motor 43r is driven and controlled by the VVE control means 123 of the ECU 100 as the control device, and the phase of the control arm 43m is determined by this driving control, and thereby the offset Since the phase of the link 43e is determined, the rotational trajectory of the intake cam 43b that drives the tappet 61 changes in the axial direction of the intake valve 40, and the valve lift amount is changed steplessly.

  With reference to FIG. 5B, the tappet 61 provided on the valve stem 40 a of the intake valve 40 is fixed to the end of the valve stem 40 a of the intake valve 40. On the other hand, the valve stem 40a of the intake valve 40 is guided by a known valve guide 40b. A spring seat portion 40c is integrally formed on the outer periphery of the valve guide 40b. The spring seat portion 40c is contracted between the spring seat portion 61a formed in the inner back portion of the tappet 61. A valve spring 40d is seated.

  The intake cam 43b is joined to the tappet 61 and receives the urging force of the valve spring 40d.

  In this state, the eccentric shaft 43k and the control arm 43m are rotated by the stepping motor 43r as shown in FIGS. 5A and 5B, and the pin 43n is eccentrically moved as shown in FIGS. 5A and 5B. When positioned below the shaft 43k, the swing angle of the intake cam 43b is increased, and a large lift control state in which the lift amount of the valve at the lift peak is the largest is achieved. Further, when the pin 43n is moved upward by the rotation of the control arm 43m or the like, the swing angle of the intake cam 43b is reduced accordingly, and the pin 43n is shown in FIGS. 5C and 5D. Is positioned above the camshaft 41a, the small lift control state with the smallest valve lift amount is achieved.

  In the large lift control state shown in FIGS. 5A and 5B, the intake cam 43b presses the tappet 61 on the tip side of the cam nose, as shown in FIG. 5B, and the intake valve 40 passes through the tappet 61. And a lift peak state (a state where the intake cam 43b greatly lifts the intake valve 40 via the tappet 61) and a lift of the intake valve 40 (the intake valve 40) as shown in FIG. It swings between the state where the amount becomes zero. Similarly, in the case of FIGS. 5C and 5D, which are in the small lift control state, swinging occurs between the lift peak state (pressing the tappet 61 on the base end side of the cam nose) and the lift amount 0 state (same as above). (See Figures (C) and (D)).

  6 schematically shows the control states of FIGS. 5B and 5D, wherein (A) corresponds to the large lift control position, and (B) corresponds to the small lift control position. 6A and 6B, the control arm 43m, the connecting link 43h, and the link arm 43i are simply represented by straight lines, and the center of the eccentric cam 43d (the center of the outer ring of the offset link 43e) is rotated. The trajectory is shown as T0.

  First, the profile of the intake cam 43b itself will be described with reference to FIG. 6A. On the peripheral surface of the intake cam 43b, a base circle surface (base circle section) θ1 having a constant curvature radius within a predetermined angle range, Following the θ1, a cam surface (lift section) θ2 having a gradually increasing radius of curvature is formed.

  6A shows the state of FIG. 5B in which the intake valve 40 is in the vicinity of the lift peak. At this time, the pin 43j is pulled up most by the connecting link 43h, and the intake cam 43b is The cam nose tip side of the cam surface θ2 is in contact with the tappet 61. On the other hand, the phantom line shows a state where the valve lift amount H is 0 (FIG. 5A). At this time, the base circle surface θ1 of the intake cam 43b is in contact with the tappet 61 and the intake valve 40 is closed. It is in a state.

  When the camshaft 41a (eccentric cam 43d) rotates in the clockwise direction in the figure, one end side (lower end side in the figure) of the offset link 43e moves along the axis X of the camshaft 41a as indicated by the arrow in the figure. Although revolving around, the displacement of the other end of the offset link 43e is regulated by a link arm 43i connected thereto. That is, the link arm 43i swings between the position of the solid line and the position of the phantom line around the pin 43n positioned below the eccentric shaft 43k, and accordingly, the other end side of the offset link 43e. The (connecting pin 43g) reciprocates around the pin 43n every time the eccentric cam 43d rotates once (the movement locus of the connecting pin 43g is indicated as T1).

  In accordance with the reciprocating arc motion T1 of the connecting pin 43g, the other end portion (pin 43j) of the connecting link 43h whose one end portion is connected to the offset link 43e by the same connecting pin 43g reciprocates along a locus indicated by T2 in the drawing. The intake cam 43b, which moves in an arc and is connected to the connection link 43h by the pin 43j, swings between the position of the solid line and the position of the phantom line in the figure. That is, when the connecting pin 43g moves upward, the pin 43j is pulled upward by the connecting link 43h, and the cam nose of the intake cam 43b pushes down the tappet 61, thereby causing the valve spring 40d (see FIG. 5B). The intake valve 40 is lifted while compressing.

  On the other hand, when the connecting pin 43g moves downward, the pin 43j is pushed downward by the connecting link 43h, and the cam nose of the intake cam 43b rises, so that the reaction force of the compressed valve spring 40d causes The tappet 61 is pushed up and moves upward so as to follow the rise of the cam nose, the intake valve 40 is pulled up, and the intake port of the intake passage 24a is closed.

  That is, in the large lift control state, the intake cam 43b swings greatly so as to press the tappet 61 by substantially the entire base circle surface θ1 and cam surface θ2 of the peripheral surface, and thus corresponds to such a large swing angle. This increases the lift amount of the valve.

  Further, from the above-mentioned large lift control state, the control arm 43m is rotated upward about the axis of the eccentric shaft 43k until it becomes substantially horizontal, as shown in FIG. 5 (D) and FIG. 6 (B), When the pin 43n, which is the rotation axis of the link arm 43i, is positioned closer to the front side in the rotational direction of the camshaft 41a than the large lift control state, the small lift control state is established. In FIG. 6B as well, as in FIG. 6A, the state where the intake valve 40 is in the vicinity of the lift peak is indicated by a solid line, and the state where the lift amount H is 0 is indicated by a virtual line.

  In FIG. 6B, when the camshaft 41a (eccentric cam 43d) rotates, the displacement of the connecting pin 43g of the offset link 43e is restricted by the link arm 43i as in the large lift control state, and the side of the eccentric shaft 43k is controlled. A reciprocating arc motion T3 is performed around the pin 43n positioned at (the link arm 43i reciprocates between the solid line position and the virtual line position in the figure). Along with the reciprocating arc motion T3 of the connecting pin 43g, the pin 43j of the connecting link 43h performs the reciprocating arc motion T4, and the intake cam 43b connected to the connecting link 43h by the pin 43j is positioned in the solid line in the figure. The intake valve 40 is opened and closed by swinging between the imaginary line and the position of the imaginary line.

  That is, in the small lift control state, the swing angle of the intake cam 43b is smaller than that in the large lift control state, and the intake cam 43b has a base circle surface θ1 on its peripheral surface and a cam surface θ2 continuous therewith. The tappet 61 is pressed only by a part, and the lift amount of the valve is reduced.

  By the VCT 42 and VVE 43 described above, the intake valve 40 is configured to be able to change the opening / closing timing and the valve lift amount H (see FIGS. 12 and 13 described later).

  Next, the VVL 70 provided in the intake valve 40 that is directly driven by the camshaft 41a will be described.

  7 is an exploded perspective view of the VVL 70 according to the embodiment of FIG. 1, FIG. 8 is a front sectional view of the VVL 70, and FIG. 9 is a plan sectional view of the VVL 70.

  With reference to these drawings, the VVL 70 is for realizing a so-called lost motion in which the function of the intake cam 43a to push down the stem 40a of the intake valve 40 is turned on / off at a predetermined timing. It is embodied in a tappet type.

  The VVL 70 includes a rectangular housing 71, a side tappet 72 that is housed in the housing 71 so as to be movable up and down, and is fixed to an end portion (stem end) of the stem 40 a of the intake valve 40. The center tappet 73 is assembled with the tappet 72 so as to be relatively displaceable and driven by the intake cam 43a.

  The housing 71 is integrated with the cylinder head 23, regulates the top dead center position of both tappets 72, 73 and the bottom dead center position of the side tappet 73, and allows the center tappet 73 to face the intake cam 43a. It is.

  The side tappet 72 is formed in a substantially cylindrical shape, and has an accommodation recess 72a in a diametrical direction perpendicular to the camshaft 41a when seen in a plan view. Each wall 72b is formed with an insertion hole 72c parallel to the camshaft 41a. The bottomed sleeve-like holders 75a and 75b are fixed to the respective insertion holes 72c in such a posture that the openings face each other. Each holder 75a and 75b is for driving the pin unit 78 accommodated in the pin hole 73a of the center tappet 73, as will be described later. A bearing 76 is fixed to the outside of one sleeve-like holder 75a (opposite side of the other sleeve-like holder 75b), and the rolling element 76a is a vertical groove 71a (see FIG. 8) formed on the inner wall of the housing 71. , See FIG. 9). As a result, the side tappet 72 is movable along the axial direction (the direction in which the intake valve 40 is opened and closed) in a state where the rotation in the circumferential direction is restricted. A spring seat 72d for receiving the valve spring 40d is fixed to the lower portion of the side tappet 72.

  On the other hand, the center tappet 73 is an “I” -shaped structure that follows the outline of the receiving recess 72 a of the side tappet 72 as viewed in plan, and is defined by the receiving recess 72 a and a locking portion provided in the housing 71. In the stroke S, the side tappet 72 is assembled so as to be movable up and down, and faces the intake cam 43a.

  The center tappet 73 is always urged toward the intake cam 43a by a pair of coil springs 77 arranged at the bottom of the housing recess 72a of the side tappet 72. The spring coefficient of the coil spring 77 is set so that the biasing force of the coil spring 77 is sufficiently smaller than the biasing force of the valve spring 40d. For this reason, in the free state, the upper surface of the wall portion 72b of the side tappet 72 and the upper surface of the center tappet 73 are flush with each other as shown in FIG. In this free state, the center tappet 73 is provided with a pin hole 73a that communicates concentrically with the insertion hole 72c. A pin unit 78 is accommodated in the pin hole 73a. The pin unit 78 includes a lock plunger 78a that can be projected and retracted in the one sleeve-shaped holder 75a, a coil spring 78b interposed between the lock plunger 78a and the sleeve-shaped holder 75a, and a lock plunger 78a. A lock pin 78c concentrically disposed on the opposite side of the coil spring 78b, and a lock release plunger that is housed in the other sleeve-like holder 75b so as to be able to advance and retreat in order to drive the lock pin 78c toward the lock plunger 78a. 78d, a pair of bushes 78e and 78f fixed to both opening ends of the pin hole 73a to support the lock pin 78c, a flange 78g and a bearing 76 integrally formed at a substantially central portion of the lock pin 78c. Between the bushing 78e on the opposite side and the flange 78g, And a coil spring 78h which urges the Kupyn 78c to the unlocked plunger 78d side. In the free state, the lock plunger 78a and the lock pin 78c are interposed between the wall 72b and the center tappet 73, respectively. Accordingly, in this state, the lock plunger 78a and the lock pin 78c lock the center tappet 73 to the side tappet 72, and when the center tappet 73 is driven by the intake cam 43a, the intake valve is connected via the side tappet 72. 40 stem 40a is pushed down and intake valve 40 is opened.

  On the other hand, in order to unlock the lock pin 78c, the other wall portion (a wall portion opposite to the wall portion 72b provided with the bearing 76) 72b, and a sleeve-like holder 75b fixed to the wall portion 72b, Is formed with a hydraulic oil passage PH. When hydraulic fluid is supplied from the hydraulic fluid circuit 79 to the hydraulic fluid path PH under the control of the ECU 100, which will be described later, the unlocking plunger 78d is driven to the left in FIGS. 8 and 9, and the lock pin 78c is moved to the wall portion. 72b is pushed into the center tappet 73, and at the same time, the lock plunger 78a is pushed into the corresponding wall 72b, and the lock by these members is released. In this unlocked state, when the center tappet 73 is driven by the intake cam 43a, the center tappet 73 moves up and down in the accommodation recess 72a of the side tappet 72, and the force is absorbed by the coil spring 77 and the intake valve 40. Is not transmitted to the stem 40a. As a result, by releasing the lock by the pin unit 78, it is possible to provide a so-called lost motion function and stop the opening of the intake valve 40 by the intake cam 43a. The hydraulic oil circuit 79 is provided with an electromagnetic valve 79a, and the electromagnetic valve 79a is controlled by the ECU 100 as a control device.

  Next, referring to FIGS. 1 and 2, the exhaust system 50 includes a bifurcated branch exhaust pipe 51 connected to an exhaust passage 24 b formed in pairs in each cylinder 24, and each branch exhaust pipe 51. An exhaust manifold 52 that collects downstream ends of the exhaust manifold 52, and an exhaust pipe 53 that discharges burnt gas from the exhaust manifold 52. The exhaust pipe 53 is provided with an oxygen concentration sensor 54.

  The exhaust system 50 includes an exhaust valve 60 provided for each exhaust passage 24b. The exhaust valves 60 are also provided in pairs for each cylinder 24. As shown in FIG. 3, also in the exhaust system 50, the above-described direct acting tappet 61 is adopted for one exhaust valve 60, and the lost motion function is provided for the other exhaust valve 60. Equipped with VVL70. As shown in FIG. 3, the VVL 70 employed in the intake system 30 and the VVL 70 employed in the exhaust system 50 are arranged in a symmetrical system around the cylinder 24. For this reason, as will be described later, when the VVL 70 of the intake valve 40 is activated and the intake valve 40 is closed, the exhaust valve 60 positioned diagonally with respect to the intake valve 40 that performs the valve opening operation is resumed. The valve can be operated.

  1 and 2, a valve mechanism 62 employed in the exhaust system 50 includes a transmission mechanism 64, a camshaft 62a driven by the driving force of the crankshaft 21 via the transmission mechanism 64, and a camshaft. 62a, two sets of cams 62b, 62c that drive the stem 60a of the exhaust valve 60 in different phases at a predetermined phase, and a VVL 70 interposed between the cams 62b, 62c and the valve stem 60a. The remaining configuration is the same as that of the valve operating mechanism 41. These cams 62b and 62c are first exhaust cams that open the exhaust valve 60 in order to discharge the burned gas in the cylinder 24 in the exhaust stroke of one of the cams 62b and 62c (the illustrated example). Then, the cam 62c) is a second exhaust cam that reopens the exhaust valve 60 at the opening timing of the intake valve 40, which will be described later, and recirculates the exhaust gas into the cylinder. In the illustrated example, the first exhaust cams 62b form a pair, and the second exhaust cam 62c is disposed between the first exhaust cams 62b and 62b in the axial direction of the cam shaft 62a. Yes.

  FIG. 10 is a front sectional view of the VVL 70 employed in the exhaust valve according to the embodiment of FIG.

  As shown in the figure, the first exhaust cam 62b is joined to the side tappet 72 of the VVL 70, and is configured to always open and close the exhaust valve 60. On the other hand, the second exhaust cam 62c is joined on the center tappet 73 so that the restart valve operation can be stopped by the control described later. In FIG. 10, 62 d is a valve spring of the exhaust valve 60. Similarly to the valve spring 40 d of the intake valve 40, the valve spring 60 d is also set to a spring coefficient that can obtain a sufficiently large urging force with respect to the urging force of the coil spring 77.

  1 and 2, between the intake system 30 and the exhaust system 50, a turbocharger 80 as a supercharger and an external part for returning the exhausted burned gas to the intake system 30 are provided. An EGR system 90 is provided.

  The turbocharger 80 is interposed in a return passage 65 formed between the intake manifold 32 and the exhaust manifold 52, and is driven by the exhaust pressure, and is driven by the turbine section 81. The compressor section 82 for introducing fresh air and the intercooler 83 for cooling the fresh air introduced from the compressor section 82 are basically used as they are. Is possible.

  The external EGR system 90 is a known system that is connected to the reflux passage 65 in parallel with the turbocharger 80 and includes an EGR cooler 91, an EGR valve 92, and an actuator 93 that drives the EGR valve 92.

  The 4-cycle gasoline engine 10 is provided with an ECU 100 as an operation control device.

  Referring to FIG. 1, ECU 100 has a CPU 101, a memory 102, an interface 103, and a bus 104 that connects these units 101 to 103.

  The memory 102 of the ECU 100 stores control maps, data, and programs based on the characteristics shown in FIGS. 11 to 15, and the CPU 101 executes these control maps, data, and programs as shown in FIG. An operation state determination unit 110 that determines the operation state and a valve control unit 120 that controls the valve operating mechanisms 41 and 62 of the intake valve 40 according to the determined operation state are functionally provided. The valve control means 120 controls the driving of the electromagnetic valves 79a and 179a, thereby switching the VVL control means 121 used for the intake system 30 and the exhaust system 50, and the intake system 30. VCT control means 122 for controlling the electromagnetic valve 42e of the VCT 42 provided in the valve operating mechanism 41 and VVE control means 123 for controlling the stepping motor 43r of the VVE 43 provided in the intake system 30 are functionally provided.

  A crank angle sensor 27, an airflow sensor 34, an oxygen concentration sensor 54, and an accelerator opening sensor 66 are connected to the bus 104 of the ECU 100 as input elements. On the other hand, as control elements, the actuator 37 of the throttle valve 36, the electromagnetic valve 42e provided in the VCT 42 of the valve operating mechanism 41, the electromagnetic valves 79a and 179a of the hydraulic oil circuits 79 and 179 that drive each VVL 70, and the intake system 30 are provided. A stepping motor 43r of the VVE 43 and an actuator 93 of the external EGR system 90 are connected.

  Next, the control characteristics stored in the ECU 100 will be described with reference to FIGS.

  FIG. 11 is a characteristic diagram illustrating an example of operation region setting for performing control according to the operation state according to the embodiment of FIG. 1.

  Referring to the figure, as an operation region set in ECU 100, a region A where so-called compression self-ignition operation (denoted as HCCI in the drawing) and a region B other than region A are set. . In the region A, a case where the engine load is equal to or lower than a predetermined engine load is set in a low / medium rotational region where the rotational speed ne is relatively low.

  In the region A, the engine load is further divided into a low load operation region A1 on the low load side and a high load operation region A2 on the high load side, and the boundary portion between them is the medium load operation region A3. .

  The operating state determining means 110 of the ECU 100 detects the operating state of the engine from the crank angle sensor 27, the accelerator opening sensor 66, and the like, and determines which operating state it is in.

  FIGS. 12 and 13 are characteristic diagrams showing the characteristics of the valve opening operation when it is determined in FIG. 11 that the region A is the region where the exhaust valve 60 is restarted.

  With reference to each drawing, in this embodiment, when it is determined that the operating state is in the region A, the valve control unit 120 opens the intake valve 40 near the top dead center and lower than the bottom dead center. The exhaust valve 60 is set to close within the period from the bottom dead center to the beginning of the compression stroke while the exhaust valve 60 is started in the middle of the intake stroke while the valve is closed before. Yes.

  Control for this setting is realized by the VVL control means 121 of the valve control means 120 controlling the electromagnetic valves 79a and 179a of the valve operating mechanisms 41 and 62, and the VVE control means 123 controlling the VVE 43 of the intake system 30. The

  Specifically, when the operation region is the region A, the VVL control unit 121 performs control so that the VVL 70 employed in the intake system 30 is unlocked and the valve opening operation is performed exclusively by the intake cam 43b. At the same time, the VVL 70 employed in the exhaust system 50 is held locked, and the restart valve operation by the exhaust valve 60 is controlled. Further, the VVE control means 123 controls the VVE 43 employed in the intake system 30 so as to change the valve opening amount by the intake cam 43b steplessly.

  Here, when it is determined that the operation state is the low load operation region A1 and the medium load operation region A3, as shown in FIG. 12, the valve lift amount (open valve amount) H of the intake valve 40 is a small lift amount. Set to Due to the cam shape of the exhaust cam 62c, the valve lift amount (valve opening amount) H during the restart valve operation of the exhaust valve 60 is approximately the same as the valve lift amount when the intake valve 40 is set to a small lift amount. Is set. In this aspect, the VCT control means 122 of the valve operating mechanism 41 opens the intake valve 40 near the top dead center (crank angle CA = 0 °), and the intake stroke is 2/3 (crank angle CA = 120 °). ) It is configured to perform a valve closing operation in the vicinity of the elapsed time. The VVE control means 123 sets the valve lift amount H to a small lift by driving and controlling the stepping motor 43r of the VVE 43 as described with reference to FIGS. .

  On the other hand, when it is determined that the operation state is the high load operation region A2, as shown in FIG. 13, the valve lift amount (valve opening amount) H of the intake valve 40 is set to a large lift amount. In this aspect, the VCT control means 122 of the valve operating mechanism 41 opens the intake valve 40 near the top dead center (crank angle CA = 0 °), and the intake stroke is 3/4 (crank angle CA = 135 °). ) After the elapse of time, the valve is closed before the bottom dead center (crank angle CA = 180 °) (for example, crank angle CA = 150 °). Further, as described with reference to FIGS. 5A, 5B, and 6A, the VVE control unit 123 sets the valve lift amount H to a large lift by drivingly controlling the stepping motor 43r of the VVE 43. .

  As described above, the valve control unit 120 according to the present embodiment has the low load operation region A1 and the medium load operation region in the high load operation region A2 in the operation region in which the restart valve operation of the exhaust valve 60 is performed according to the engine load. Control means for controlling the valve operating mechanism 41 as intake valve drive means is configured so that the valve lift amount H of the intake valve 40 becomes larger than A3.

  Here, in the present embodiment, in the low load operation region A1, one intake valve 40 is stopped by the VVL 70 and the control valve 79a as valve closing means, and only the intake cam 43a drives the tappet 61, thereby In addition to performing the operation, the exhaust valve 60 (exhaust valve 60 on the side where the VVL 70 is disposed in FIG. 3) located on the diagonal line with respect to the intake valve 40 that performs the valve opening operation is restarted. The valve mechanism 41 and the VVE 43 are configured. Therefore, in the present embodiment, in the low load operation region A1, the one intake valve 40 is closed and the exhaust valve 60 positioned diagonally with respect to the intake valve 40 that performs the valve opening operation is restarted, so that the intake air Sometimes swirl occurs. As a result, the air-fuel mixture in the cylinder 24 is disturbed, and the mixing of fresh air introduced from the intake passage 24a and burned gas introduced from the exhaust valve 60 is promoted. For this reason, a rapid temperature rise can be achieved, and compression self-ignition can be performed more reliably. Moreover, since the mixing with the fuel is promoted by the disturbance, the fuel efficiency is improved and the lean combustion limit is also improved.

  When it is determined that the operation region is the region B, the VVL control unit 121 holds the lock of the VVL 70 employed in the intake system 30 and opens the valve by both the intake cams 43a and 43b. While controlling, the lock | rock of VVL70 employ | adopted by the exhaust system 50 is cancelled | released, and the restart valve operation | movement by the exhaust valve 60 is stopped. This makes it possible to obtain a general operation mode.

  When the valve opening operation is controlled with the settings shown in FIGS. 12 and 13, the in-cylinder temperature Tp, the boost pressure P, the charging efficiency ηv, and the internal EGR rate m near the compression top dead center are shown in FIGS. 14 and 15, respectively. It becomes the characteristic shown by.

  FIG. 14 is a graph showing the relationship between the in-cylinder temperature Tp, the charging efficiency ηv, and the internal EGR rate m near the compression top dead center with the boost pressure P as the horizontal axis, and FIG. It is the graph which showed the relationship between the cylinder temperature Tp in the vicinity of a compression top dead center, and the boost pressure P as an axis | shaft. In each graph, the subscript L is the operating state in the low load operation region A1 and the medium load operation region A3 based on the characteristics of FIG. 12, and the subscript H is the high load operation region A2 based on the characteristics of FIG. It shows that it is a characteristic of the driving state.

As shown in FIG. 14, in the relationship between the change rate of the boost pressure P and the in-cylinder temperature Tp, the in-cylinder temperature Tp decreases as the boost pressure P increases in any of the characteristics of FIGS. The in-cylinder temperature Tp is lower when the characteristic of FIG. 13 is adopted, and the in-cylinder temperature Tp is higher when the characteristic of FIG. 12 is adopted. . This is because, in the characteristics of FIG. 12, the burned gas is easily introduced into the cylinder 24 during the restart valve operation of the exhaust valve 60, thereby increasing the internal EGR rate m ₍ see the internal EGR rate ml in FIG. 14). This is because, in the intake stroke, coupled with the fact that the intake valve 40 opens with a small lift amount, the amount of fresh air introduced is limited, and the in-cylinder temperature tends to increase. As a result, in this embodiment, the in-cylinder temperature Tp in the low load operation region A1 and the medium load operation region A3 is maintained at a relatively high temperature, and a reliable compression self-ignition can be realized while reducing the pumping loss. It becomes possible.

  On the other hand, in the characteristics shown in FIG. 13, since the intake valve 40 is opened with a large valve lift during the intake stroke, new air is easily introduced, and the EGR rate is relatively reduced. Here, in the high load operation region A2, the ECU 100 in the present embodiment is set to close the multiple throttle valve 36 to reduce the amount of fresh air and increase the external EGR rate. Thereby, the external EGR system 90 as the external EGR means can be coupled with introducing a large amount of relatively cold external EGR gas into the cylinder, reducing the in-cylinder temperature Tp and suppressing knocking.

  Referring to FIG. 15, the relationship between the charging efficiency ηv and the boost pressure P shows that the internal EGR rate m is high in the characteristics of FIG. 12, so that the lower charging efficiency ηv ( Engine load). Here, the ECU 100 in the present embodiment is set to open the multiple throttle valve 36 in the low load operation region A1 and the medium load operation region A3. Thereby, pumping loss can be reduced and fuel consumption can be improved.

  On the other hand, in the characteristics of FIG. 13, the internal EGR rate m is suppressed, the charging efficiency ηv for the same boost pressure P is high, and the charging efficiency ηv due to fresh air is given priority. Therefore, a high filling efficiency ηv can be ensured at a high boost pressure P close to atmospheric pressure. Therefore, in the high load operation region A2, the burned gas is prevented from being blown back into the intake passage 24a, and combined with the cooling effect by the fresh air, it is possible to prevent knocking. Furthermore, in this embodiment, by changing the valve lift amount of the intake valve 40 to a large valve lift, it is possible to introduce a large amount of relatively low-temperature external EGR gas by the external EGR system 90, thereby further suppressing knocking. Will contribute.

  Here, as shown by the phantom line Ps in FIG. 15, in this embodiment, the stepping motor 43 r of the VVE 43 described above is controlled steplessly, and as the engine load gradually increases, the characteristics of FIG. The VVE control means 123 of the valve control means 120 is set so as to shift to the characteristics shown in FIG. This makes it possible to execute intake / exhaust control of the engine with optimum characteristics for each operating state.

  As described above, in the present embodiment, when the exhaust valve 60 is restarted during the intake stroke, the valve mechanism 62 as the exhaust valve driving means is opened during the intake stroke and compressed from near the bottom dead center. Since the valve is closed within the period until the initial stage of the stroke, the exhaust valve drive means suppresses the discharge of fresh air from the exhaust passage 24b and suppresses the discharge of burned gas to the intake passage 24a side. Therefore, the exhaust valve 60 restarts during the intake stroke and closes in the period from the bottom dead center to the beginning of the compression stroke. In this valve opening operation, the exhaust valve 60 is discharged during the exhaust stroke. The burned gas can be introduced into the cylinder 24 in a relatively large amount as internal EGR gas. Thereby, in a state where the boost pressure P (intake pressure) is as high as possible (a state close to the atmospheric pressure side), the range in which the charging efficiency ηv and the internal EGR rate m change is expanded, and according to the change in the engine operating state, The required charging efficiency ηv suitable for the engine load and the appropriate internal EGR rate m can be ensured. As a result, the compression self-ignition performance in the compression stroke can be improved while reducing the pumping loss. Moreover, since the structure which opens the exhaust valve 60 in the intake stroke is employ | adopted, internal EGR is realizable at the timing which the exhaust valve 60 does not interfere with a piston. Therefore, the geometric compression ratio can be increased as much as possible (for example, compression ratio = 12). In the present embodiment, the VVE 43 is controlled by the valve control unit 120 (more specifically, the VVE control unit 123) as a control unit, so that the exhaust valve 60 is restarted according to the engine load. In the high load operation region A2 in the operation region A, the valve lift amount H of the intake valve 40 is larger than that in the low load operation region A1 and the medium load operation region A3. It is possible to reduce the amount of gas introduced and suppress an excessive increase in the in-cylinder temperature Tp. As a result, it is possible to expand the region where compression self-ignition is possible to the high load operation region A2 as much as possible.

  Particularly in the present embodiment, at least in the high load operation region A2 of the operation region in which the restart valve operation of the exhaust valve 60 is performed, the valve lift amount H of the intake valve 40 is set to the valve lift amount H by the restart valve operation of the exhaust valve 60. It is set to be larger. Therefore, in the present embodiment, since the amount of fresh air can be ensured in the high load operation region A2, it is possible to ensure the charging efficiency ηv while suppressing the return of burned gas to the intake passage 24a. it can. Further, since a large amount of fresh air is introduced, the in-cylinder temperature Tp can be reduced, which contributes to suppression of knocking.

  Further, in the present embodiment, as described with reference to FIGS. 12 and 13, the valve lift amount H of the intake valve 40 is set to the restart valve operation of the exhaust valve 60 within the operation region A in which the restart valve operation of the exhaust valve 60 is performed. The ratio between the two is changed in accordance with the operation state while the valve lift amount is not less than H. Therefore, in this embodiment, the internal EGR rate m and the charging efficiency ηv can be adjusted according to the operating state. Therefore, on the high load side, the charging efficiency ηv can be increased while reducing the internal EGR rate m. In addition, in the low load operation region A1, it is possible to increase the internal EGR rate m and increase the in-cylinder temperature Tp, thereby improving the compression self-ignition performance. Therefore, it is possible to maintain the optimal internal EGR rate m and filling efficiency ηv according to the individual operation regions.

  Further, in the present embodiment, an external EGR system 90 is provided as an external EGR means for returning the exhaust gas cooled via the recirculation passage (external EGR passage) 65 to the intake system 30, and the resuming valve operation of the exhaust valve 60 is performed. In the operation region where knocking is likely to occur, that is, the high load operation region A2, the internal EGR rate m by the external EGR system 90 is increased. Therefore, in this embodiment, by introducing a relatively cool external EGR gas into the cylinder 24 by the external EGR system 90, the in-cylinder temperature Tp can be reduced and knocking can be suppressed.

  Further, as described with reference to FIG. 15, the valve control unit 120 of the present embodiment has a high load in the low load operation region A1 and the medium load operation region A3 in the operation region A in which the restart valve operation of the exhaust valve 60 is performed. The valve operating mechanism is such that the valve lift amount H of the intake valve 40 is made smaller than the operation region A2, and the valve lift amount H of the intake valve 40 is gradually increased as the operation shifts from the medium load operation region A3 to the high load operation region A2. 41 and 62 are controlled. In the present embodiment, in the low-load operation region A1 and the medium-load operation region A3, although the change rate of the boost pressure is large with respect to the charging efficiency ηv, the internal EGR rate m is increased and the cylinder temperature Tp is increased. It is possible to achieve reliable compression self-ignition and reduce pumping loss. On the other hand, in the high load operation region A2, the charging efficiency ηv is reduced while preventing knocking by suppressing the internal EGR rate m and the accompanying temperature rise by making the change rate of the boost pressure small with respect to the charging efficiency ηv. Can be increased. Here, in the present embodiment, the valve control mechanism 120 is configured so that the valve control mechanism 120 gradually increases the valve lift amount H of the intake valve 40 as it shifts from the medium load operation region A3 to the high load operation region A2. Since the control is performed, it is possible to smoothly switch the balance between the in-cylinder temperature Tp and the charging efficiency ηv and obtain an optimal control state according to the operating state.

  As described above, according to the present embodiment, in realizing the compression self-ignition in the 4-cycle gasoline engine 10, the mechanical compression ratio is increased as much as possible, and the boost pressure P is increased as much as possible. By expanding the change range of the efficiency ηv, the pumping loss is reduced according to the change in the operating state of the engine, and the necessary charging efficiency ηv suitable for securing compression self-ignition and torque and the appropriate internal There is a remarkable effect of securing the EGR rate m.

  The above-described embodiments are merely preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments.

  FIG. 16 is a schematic plan view schematically showing one of cylinders according to another embodiment of the present invention, and FIG. 17 is a perspective view schematically showing a valve mechanism of an intake system corresponding to the same embodiment. It is.

  First, referring to FIG. 16, in the illustrated embodiment, when two intake valves 40 and two exhaust valves 60 are provided per cylinder, the intake system 30 does not employ VVL, Is also equipped with a direct-acting tappet 61. On the other hand, as shown in FIG. 17, the intake cams 43a and 43b that drive the tappets 61 of the intake valves 40 are integrated via a cam journal 43c.

  The VVE control means 123 in this configuration is configured to set the valve lift amount H to the maximum lift amount during operation in the region A, and to increase or decrease the valve lift amount H according to the engine load during operation in the region A. Is done.

  In this configuration, unlike the embodiment of FIG. 1, the valve opening operation that gives a swirl effect cannot be performed, but a hydraulic mechanism for controlling VVL or VVL is not required in the intake system 30, so the configuration in terms of hardware is not required. It becomes possible to simplify and reduce the cost.

  In addition, it goes without saying that various modifications are possible within the scope of the claims of the present invention.

1 is a configuration diagram illustrating a schematic configuration of a four-cycle gasoline engine according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the structure of one cylinder of the engine body according to FIG. 1 and intake and exhaust valves provided for the cylinder. FIG. 2 is a schematic plan view of an intake valve and an exhaust valve provided in a cylinder according to the embodiment of FIG. 1. It is a perspective view which shows the specific structure of the valve mechanism which concerns on embodiment of FIG. FIG. 5 is a cross-sectional view showing the main part of the VVE in FIG. 4, (A) shows when the lift amount is 0 in the large lift control state, (B) shows when the lift amount is maximum in the large lift control state, (C) shows when the lift amount is 0 in the small lift control state, and (D) shows when the lift amount is maximum in the small lift control state. FIGS. 5B and 5D schematically represent the control states, where FIG. 5A corresponds to the large lift control position, and FIG. 5B corresponds to the small lift control position. It is a disassembled perspective view of VVL which concerns on embodiment of FIG. It is front sectional drawing of the same VVL. It is a plane sectional view of the same VVL. It is front sectional drawing of VVL employ | adopted as the exhaust valve which concerns on embodiment of FIG. It is a characteristic view which shows an example of the driving | operation area | region setting for performing control according to the driving | running state which concerns on embodiment of FIG. In FIG. 11, it is a characteristic view which shows the characteristic of the valve opening operation | movement when it determines with the area | region which performs the restart valve operation | movement of an exhaust valve. In FIG. 11, it is a characteristic view which shows the characteristic of the valve opening operation | movement when it determines with the area | region which performs the restart valve operation | movement of an exhaust valve. It is the graph which showed the relationship between the cylinder temperature in the vicinity of a compression top dead center, filling efficiency, and an EGR rate by making a boost pressure into a horizontal axis. It is the graph which showed the relationship between the cylinder temperature in the vicinity of a compression top dead center, and a boost pressure on the horizontal axis of charging efficiency. FIG. 6 is a schematic plan view schematically showing one of the cylinders according to another embodiment of the present invention. It is a perspective view which shows roughly the valve operating mechanism of the intake system corresponding to the embodiment.

Explanation of symbols

10-cycle gasoline engine 20 engine body 21 crankshaft 22 cylinder block 23 cylinder head 24 cylinder 24a intake passage 24b exhaust passage 25 piston 26 combustion chamber 27 crank angle sensor 28 fuel injection valve 29 spark plug 29a ignition circuit 30 intake system 40 intake valve 41 Valve mechanism 50 Exhaust system 60 Exhaust valve 62 Valve mechanism 62b Cam (an example of a first exhaust cam)
62c cam (example of second exhaust cam)
70 VVL
90 External EGR system 100 ECU (an example of an operation control device)
110 Operating state determination means 120 Valve control means (an example of control means)
121 VVL control means 122 VCT control means 123 VVE control means A area (an example of an area where the restart valve operation is performed)
A1 Low-load operation area A2 High-load operation area A3 Medium-load operation area (boundary part)
P Boost pressure H Valve lift amount m Internal EGR rate ηv Filling efficiency

Claims (7)

In the predetermined engine operating range, in addition to the valve opening operation during the exhaust stroke, the resuming valve operation for reopening the exhaust valve during the intake stroke increases the in-cylinder temperature by internal EGR and causes compression self-ignition to occur. In a 4-cycle gasoline engine,
An exhaust valve driving means for opening the valve during the intake stroke during the restart valve operation of the exhaust valve, and closing the valve within a period from the bottom dead center to the beginning of the compression stroke;
At least in the operating range where the exhaust valve is restarted, the intake valve can be changed while the intake valve is opened near top dead center and closed before bottom dead center Intake valve drive means to
According to the engine load, the intake valve driving means is controlled so that the opening amount of the intake valve is larger in the high load operation region of the operation region in which the restart valve operation of the exhaust valve is performed than in the low load operation region. And an intake / exhaust control apparatus for a four-cycle gasoline engine. The intake / exhaust control apparatus for a 4-cycle gasoline engine according to claim 1,
The opening amount of the intake valve is set to be larger than the opening amount due to the restart valve operation of the exhaust valve in at least the high load operation region of the operation region where the restart valve operation of the exhaust valve is performed. An intake / exhaust control system for a 4-cycle gasoline engine. The intake / exhaust control apparatus for a 4-cycle gasoline engine according to claim 2,
Within the operating range where the restart operation of the exhaust valve is performed, the valve opening amount of one intake valve is equal to or greater than the valve opening amount due to the restart valve operation of the exhaust valve, and the ratio of both changes according to the operating state An intake / exhaust control system for a four-cycle gasoline engine, characterized in that The intake / exhaust control device for a 4-cycle gasoline engine according to any one of claims 1 to 3,
The external EGR means for recirculating the exhaust gas cooled through the external EGR passage to the intake system, and in the operation region where knocking is likely to occur in the operation region where the restart valve operation of the exhaust valve is performed, the external EGR is performed. An intake / exhaust control system for a four-cycle gasoline engine, characterized in that the EGR amount by the means is increased. The intake / exhaust control apparatus for a 4-cycle gasoline engine according to any one of claims 1 to 4,
The control means reduces the opening amount of the intake valve in the low load side operation region of the operation region in which the resumption valve operation of the exhaust valve is performed, with respect to the boundary between both operation regions. Intake and exhaust of a four-cycle gasoline engine, wherein the intake valve driving means and the exhaust valve driving means are controlled so as to gradually increase the valve opening amount of the intake valve as it shifts from the operating range to the operating range on the high load side. Control device. The intake / exhaust control apparatus for a 4-cycle gasoline engine according to any one of claims 1 to 5,
Two intake valves and two exhaust valves are provided per cylinder, and in the low load operation region of the operation region in which the exhaust valve is restarted, one intake valve is stopped by the closing means and the valve is opened. An intake / exhaust control apparatus for a four-cycle gasoline engine, characterized in that an intake valve drive means and an exhaust valve drive means are configured to restart the exhaust valve located diagonally with respect to the intake valve that operates. The intake / exhaust control apparatus for a 4-cycle gasoline engine according to any one of claims 1 to 6,
The exhaust valve driving means includes: a first exhaust cam that opens the exhaust valve during an exhaust stroke; a second exhaust cam that opens the exhaust valve during an intake stroke; and lost transmission that can cut off drive transmission from the second exhaust cam to the exhaust valve. With a motion mechanism,
The intake valve driving means includes a valve opening variable mechanism that allows stepless change of at least one of a valve lift amount and a valve opening period of the intake valve. .

Images